Relay system



G. P. WILSON.

RELAY SYSTEM. APPLICATION FILED JAN- 20. I921.

I mma Mar. 21, 1922.

'. ATTORNEY INVENTOR o/cgg r Mi/son ootnnn P. winson, OFWILKINSBURG,PENNSYLVANIA;ASSIGNORITOWESTINGHOUSE ELECTRIC &MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

, RELAY SYSTEM. 7

Specification of Letters I'atent, Patented B131. 21, 1922.

Application fi led l'anua ry 20, .1921. Serial 1%. 438,666.

To all whom it may concern:

Be it known that I, Gononn RNVILsoN, a citizen of the United States, anda] resident of lVilkinsburg, in thecounty of Allegheny and State ofPennsylvania, have inventeda new and useful Improvement in Relay Systems, of whichthe following is a specifica} tion. c p j v Myinventionrelates to protective relay systems and particularly to relaysystems for the protection of rolling mills.

One object of my invention is to, provide means for precluding thedisconnection of an electrically-operated rolling-mill motor from asource of energy before the operation of the rolling mill has beencompletechif a fault, other than a low-resistance short circuit, shouldoccur in the circuit that would tend to effect the disconnection oftherollingmill motor. i

Another object of my invention to provide means,of the above-indicatedcharacter, that shall preclude the disconnection of'an operatingapparatus from an energizing source before the operation of theapparatus has, been completed. Another object'ot my invention is toprovide means, of the above-indicatedcharacter, that shall be simple andinexpensive inconstruction and reliable in its operation.

The stopping of a rolling mill before the completion of its operationisextremely undesirable because of the damage that is normally causedbythe hot metalthat is being shaped or formed by'the' rolls of: themill. If, for any reason, the mill is. stopped while the hot metal isbetween the rolls, unlessthe metal is quickly removed, the uneven heatinof the rolls causes them to crack; Consi erable time is then required toremove the rolls and the heated'metal, and great expense is incurredthereby. p v

Uponthe occurrence of a ground in the feeder circuit that suppliesenergy to a roll= ing-niill motor, itis desirable to disconnect thatmotor from the system until the ground may be located and cleared inorderto prevent the development of a short circuittherefrom. For thereasons stated. above, however, it is essential that the motor shouldnotbe disconnected before the operation of the mill has been completed. g

In. my co-pending application,"Serial No.

' 410,933, filedSept. 17, 1920, o f which this is a'contin'uation inpart, I describe a relay system to take care of the above-mentionedconditions. V

Inqaddition to the over load relays that are normally employed forprotection against a short-circuit conditions, I provide a ground relay:which is responsive only to'current-s that are causedby a groundon thecircuit. Upon the occurrence of'a ground, the ground relay energizes atime-limit relay, the time element) of which exceeds the time intervalrequired fort-he operation'of the rolling millj Thedefinite timeelementrelay, in"

turn, eilectsthetripping of the circuit interrupter to disconnect therolling mill from the sourceof energy. i

, In the system disclosed in the co pending application, I provide anindicating device to indicate to the 'operatorthat the circuit I ofv hismillhas become grounded. Upon the occurrence of such condition, the millshould not be restarted until the fault has been cleared. I

J "If, however, the indicating device should 1 become cfaultyand' failto operate. or if the operator should neglect to heed theindicationthefault and should start the mill for another operation, the timeinterval of the relay might so overlap the interval between theoperationsQof the millthat the inter; rupter would be tripped .while themill was operating.

: In 'order toprevent absolutely the tripping of an interrupter whilethe mill is operating, I providepa'ccording to my present invention, anaddltional relay, that is energized "while the mill operating, tomaintain the tripping circuit open until, the operation of the mi11 'iscompleted. The inill motor is, therefore, disconnected if thetime-element relay isinjits operative position.

;The single 'fig'urePof the accompanying drawing is a diagrammatic view,of an electrical" system embodying my invention.

4 Y source flj'of "electromotive' 1 force; is adaptedto'supply energy toa circuit 2 from which ene rgymay be suppliedto a rolling mill'motor 3-through a circuit interrupter- 4. The interrupter 4 is provided with atripping device 5 having an energizing winding 6, the circuit-of whichis controlled by a timeelement relay 7 I I CIT The rolling-mill motor issupplied with energy through a feeder circuit 8 that has a plurality ofcurrent transformers 9, l and 11 so connected thereto as to be traversedby currents that are proportional to the currents traversing theconductors of the circuit 8.

A plurality of overload relays 12,13 and i i are connected to thecurrent transformers 9, and 11, respectively, and a ground relay 15 isso connected in the neut 'all conductor joining the current transformersand theoverload relays as to be traversed by only such currents as maybe caused to traverse the circuit by reason of a ground thereon. Theenergization of the ground relay 15 effects engagement between itscontact members 16 and 17, completing a circuit thereby from negativeconductor 18 of a source of electromotive force 19, through theenergizing winding 20 of the relay 7, to the positive conductor 21 ofthe source 19 of electromotive force.

The time-element relay 7 is further provided with a device 22 thatembodies a time element exceeding, in value, the interval of time thatis required for the complete operation of the rolling mill. Anindicating device 28, such as a lamp or a bell alarm. is provided toindicate to the operator of the rolling mill that there is a ground onthe feeder circuit which is connected to that rolling mill.

Simultaneously, the operator at the generating station is notified ofthe occurrence of a ground by an indicating device or bell alarm 24, thecircuit of which is con-trolled by a relay 25. The relay 25 is energizedfrom a current transformer 26 that is connected in a ground conductor 27and is energized only upon the occurrence of a ground on the system thatcauses" a current to traverse the ground conductor 27.

If the indicating device 23 should become inoperative and fail toindicate the occurence of a fault, or if the operator should fail to seethe indicating device 2 he might start the mill for another operation,and the operation of the relay 7 might trip the interrupter 4.- whilethe mill would be operating.

In order to prevent such an occurrence, a relay 28 is provided that willbe energized while the mill is operating to maintain the trip circuit ofthe interrupter open. While the motor 3 is operating, the coil 29oitythe relay 28 raises the switch 30. A latch 31 maintains it in thisopen position until the latch is released by a reset coil 32.

The relay 7 is provided with a switch 33 and an auxiliary switch 34 thatis closed prior to the closure of the switch 33 when the relay isoperated.

-Thus, if a ground occurs near the com pletion of an operation, therelay 15 causes the initiation of the relay 7. Assuming that theoperator starts the mill motor for another operation, the switch 34;will complete the energizing circuit of the reset coil 32 to release therelay 28 to close the switch 30. However, since the coil 29 will heenergized while the motor is operating, the switch will be maintainedopen. The latch, meanwhile, is rendered inoperative by the reset coil32. Upon the completion of the mill operation, the switch 30 ispermitted to close, and the interrupter l is automatically tripped. Therelay 28 thus absolutely prevents the tripping of the interrupter uponthe occurrence of a ground in the circuit while the mill is operating.

The alarm at a rolling-mill-operating pulpit is arranged to be energizedwhen the ground relay 15 that is associated with that mill is energized.The relay 7 may be arranged to maintain the tripping winding 6 energizeduntil the relay 7 is reset after the ground has been cleared, or, therelay '7 may be rendered automatically self-resetting.

It is obvious that only the rolling-mill motor which is connected to thefaulty feeder will be disconnected from the circuit 2 in a system whichembodies a plurality of rollingmill motors 3. The circuit 2 may beremotely disposed with respect to the source 1 of electromotive force,as in the relation between a substation and the main generating station.

Upon the occurrence of a ground on the conductor 35, the currenttransformers 9 and 26 are traversed by a grountl current which energizesthe relays 15 and 25. The relay 15 effects the energization of theindicating device 23 at the rolling-mill-operating pulpit and alsoinitiates the operation of the relay 7 to actuate the interrupter afteran interval of time if the motor is not then operating. Simultaneously,the bell alarm 2 1 at the gencrating station is energized by theoperation of the relay 25,. V

The disconnection of the rolling mill motor before the operation of themill completed is thus prevented by the, relay 28 which maintains thecircuit of the trip coil open while the mill is operating. Thereconnection of a rolling-mill motor on a grounded feeder circuit to thesupply circuit may be prevented until the relay is reset manually, ifthe relay 7 is arranged to maintain the tripping winding 6 of theinterrupter energized. Y

The overload relays 12. and 14 are so adjusted as to be operated bycurrents of ex tremely large values only. such as would result upon theoccurance of short-circuit conditions. Under such conditions,theoperation of the motor and, consequently, of the rolling mill couldnot be completed, and the relays are, therefore, arranged to effect thetripping of the interrupter.

My invention is not limited to the specific arrangement or to thedevices shown, as various modifications may be made therein with anapparatus requiring afdeiiniteinterval of time for the operation thereofand a circuit interrupter therefor, of means energizednpon theoccurrence of a fault 1n the circuit for actuating the interrupter,means for controlling the actuating means in ac cordancewith the timerequired for'the operation of the apparatus, and means for rendering"the controlling means inoperat ve while the apparatus is operatin .2. Inan electric circuit, the combination with an apparatus requiring adefinite interval of'time for. the operation thereof and a circuitinterrupter therefor, of meansenergized upon the occurrence of afault'inthe circuit, means having a definite time interval in the operationthereof, and controlled by the fault-energizedmeans for actuating theinterrupter, and mfeans for rendering the actuating means inoperativewhile the apparatus is operating. 7

3. In-an electric circuit,the combination withan apparatus requiring adefinite interval of time for the operation thereof and a circuitinterrupter therefor, of means energized upon the occurrence of a faultin the circuit, means, having a definite time interval in the operation'thereof,controlled the fault-energized means foractuating theinterrupter, and means for, precluding the actuationof the interrupterby the definite time means while the apparatus is operating.

4-. In an electric circuit, the combination with an apparatus requiringa definite interval of time for the operation thereof and a circuitinterrupter therefor, of means energized upon the occurrence of a faultin the circuit, means controlled thereby for actuating the interrupterafter an interval of time greater than that required for the operationof the apparatus, and means for automatically extending the timeinterval, whenever necessary, until an operation has been completed.

5. In an electric circuit, the combination with a feeder circuit, arolling mill for that circuit requiring a definite interval of time forthe operation thereof and a circuit interrupter for the circuit, ofmeans for actuating the interrupter, means for controlling the time ofoperation of said means, and means for ensuring that the actuation ofthe inter rupter by said means shall occur only when the apparatus hascompleted an operation and is not operating.

6. In an electric circuit, the combination with a feeder circuit, arolling mill therefor requiring a definite interval of time for theoperation thereof, and a circuit interrupter for the feeder circuit, ofmeans for actuating; the interrupter, means for controlling, theactuating means having a time interval greater than that required forthe operation of the rolling mill, and means for extending the timeinterval to the end of an operation, if the interval should he completedwhile the mill is operating. 1

, 7 In an electric circuit, the'comhination with a. feeder circuit, arolling mill requiring a definite interval of time for the operationthereof, and a circuit interrupter for the feeder circuit, of means foractuating the interrupter, means for controlling the actuating meanshaving a time interval greater than that required for'the operation oftherolling mill, and meansencrgized while the apparatus is operatinq toprevent the actuation of the" interrupter until its op era'tion has beencompleted.

8. In electric circuit, the combination with a feeder circuit,arollingmill for that circuitrequiring a definite interval of timeforthe'operation thereof and a circuit interrupter for the feedercircuit, of means for actuatingthe interrupter, means for controllingtheactuating means having a time interval greater than that required forthe operation of the rolling mill, and means for malntaining theinterrupter-actuatingmeans inoperative while the apparatus is operating.In an electric circuit. the combination with an amoaratus" rerpiiring adefinite interyal of time for'the operation thereof,and V a circuitinterrupter therefor, of means ener- ,QlZQfl upon the occurrence of avfaultin the circuit for "actuating the interrupter, and means energizedwhile the apparatus .is in. operation to maintain the actuating meansinoperative during that time.

10. The combination with a rolling mill, a motor therefor, a source ofenergy for the motor and means for connectingthe motor to the source ofenergy, of means for controlling the disconnection of the motor from thesource of energy upon the occurrence of a faulty condition in saidsource and means for rendering the controlling means ineffective duringan operation of. the rolling mill. 7 i

11. The combination with a rolling mill. a motor therefor, a source ofenergy for the motor and means for connecting the motor to the source ofenergy, of means responsive to an abnormal condition of the connectingmeans, and means responsive to the operating currentof the motor whilethe mill is operatlng, said means co-operatimq to control thedisconnection of the motor from its source of energy after theoccurrence of a faulty condition in the connecting means and after thecompletion of the operationof the rolling mill during which the faultycondition occurred.

12. The combination with an apparatus op erating continuously through apredetermined cycle, a motor for actuating the same, a source of energyfor the motor, and a con necting device between the motor and the sourceof energy, of a relay responsive to the motor current and a relayresponsive to a predetermined abnormal condition in the source of energyor in the motor, for actu ating the connecting device only after theapparatus has completed its operation through the predetermined cycle.

13. The combination with .an apparatus operating continuously through apredetermined cycle, a motor for actuating the same, a source of energyfor the motor, and a connecting device bet-ween the motor and the sourceof energy, of means responsive to the operating current of the motor forcontrolling the connecting device to disconnect the motor from thesource or energy only after the operation of the apparatus has beencompleted.

14. The combination with an apparatus operating continuously through apredetermined cycle, a motor for actuating the same, a source of energyfor the motor, and a connecting device between the motor and the sourceof energy, of means responsive to the operating force of the motor forcontrolling the connecting device to disconnect the motor from thesource of energy after the completion of an operation during which anabnormal condition has occurred in the source of energy or in the motor.

15. In an electric circuit, the combination with a motor energizedtherefrom and adapted to operate continuously through a predeterminedoperation, and a circuit-controlling device therebetween, of meansresponsive to the condition of the circuit and the motor and to thecurrent traversing the motor for controlling the circuit-controllingdevice only after the completion of an operation during which anabnormal or faulty condition should occur in the circuit or the motor.

16. The combination with an apparatus adapted for continuous operationduring a predetermined cycle, an electric motor therefor and a source ofenergy for the motor, of means for disconnecting the motor from itssource of energy upon the occurrence of .a fault in the motor or in thesource of energy, and means for rendering the disconnecting meansinoperative until the apparatus has completed the operation involved inthe predetermined cycle.

17 In an electric circuit, the combination with a motor operating anapparatus adapted to be loaded during a predetermined operation thereof,of means for disconnecting the motor from the circuit and means forprecluding such disconnection except when the apparatus is unloaded.

18. The combination with a continuously operating apparatus that isloaded at different times to perform predetermined operations, of amotor therefor, a source of energy for operating the motor, means fordisconnecting the motor from its source of energy and means forprecluding such disconnection while the apparatus is perform-- inganoperation.

In testimony whereof, I have hereunto subscribed my name this 11th dayof J an uary, 1921.

GOLDER P. WVILSON.

